In association with an increase in demand for a wideband multimedia communication service, such as the Internet and image distribution, introduction of an optical fiber communication system that covers a long distance and that has a large capacity has been progressing in trunk line networks and metro access networks. In such an optical communication system using optical fibers, it is important to increase transmission efficiency per optical fiber. For this reason, wavelength division multiplex (WDM) communication, in which a plurality of optical signals having different wavelengths are multiplexed and transmitted, are widely used.
Optical transmission devices are required to perform transmission over a longer distance than that conventionally covered and to have operational flexibility because of an increase in information communication traffic in recent years, and research and development in elastic optical technology has been conducted.
PTL 1 and NPL 1 disclose technologies relating to optical transmission devices that are capable of autonomously changing a pass band for optical signals while being in operation in an optical network using a WDM technology.